1. Field of the Invention
This invention relates to the production of high purity phenol, particularly to a process for reduction of levels of methylbenzofuran in phenol to obtain desired high purity.
2. Description of Related Art
Phenol may be produced from cumene by the oxidation of cumene to cumene hydroperoxide, followed by cleavage or decomposition of the hydroperoxide to phenol and acetone. The reaction product is introduced into a separation and recovery system wherein acetone is separated from remaining product by distillation. The remaining product is then further distilled to separate cumene. The cumene recovery column can be operated if desired to recover alpha-methylstyrene (AMS) with the cumene, or the product remaining from the cumene recovery column may be introduced into a crude AMS column to separate AMS from the remaining product. The remaining product is introduced into a phenol recovery column to separate phenol from remaining higher boiling constituents.
The phenol product obtained by fractional distillation includes many impurities including AMS, acetol (hydroxyacetone), acetophenone, cumylphenols and 2- and 3-methylbenzofuran (collectively or individually MBF). For certain purposes it is important to reduce such impurities to avoid problems with discoloration on aging or on sulfonation or on chlorination. Since MBF and phenol have similar volatility, MBF cannot be separated effectively by fractional distillation. Distillation in the presence of water, or steam stripping, has been disclosed in U.S. Pat. Nos. 5,064,507 and 4,857,151 to reduce the amount of MBF. Such steam stripping requires substantial expenditure of energy to produce the necessary amount of steam and the use of large distillation columns to accommodate the flow of the organic vapors and the added steam. Thus removal of MBF by steam stripping is expensive in terms of operating cost and capital investment. U.S. Pat. No. 3,810,946 discloses reduction of MBF impurities by heating phenol with hydrobromic or hydroiodic acid. Treatment with halogenated compounds, however, leads to problems with corrosion which adds substantially to the cost of materials of construction.
The need exists for an effective and economical process to reduce the level of MBF in phenol to obtain desired high purity phenol.